Can Islamic State really be defeated in months?

You may have heard a claim being made that Islamic State militants (IS) could be beaten within months, or even weeks, if certain things happen.

Masrour Barzani said it. He's the head of intelligence and security in Iraqi Kurdistan and has called the Paris attacks a "wake-up call" for Western nations.

But he reckons the group, responsible for brutal terrorist attacks and mass killings, can be overcome if the world community becomes fully engaged.

Barzani's troops are fighting IS in the Kurdish region of Iraq which means getting more international help is in his interests.

Since Friday, France has stepped up its bombing campaign against IS - as has Russia.

Britain's already involved in US airstrikes in Iraq but David Cameron now says he wants to join the fight in Syria too.

The prime minister has previously said it could take a generation to beat the militants.

So who is right? Natasha Underhill, lecturer specialising in IS at Nottingham Trent University, answers some of the big questions.

Just how active is IS in Syria and Iraq?

"America's Central Intelligence Agency estimates there are 40,000 core fighters.

"That doesn't sound that much but we can see how significant an impact those fighters have had... they're able to outrun us in a number of key areas.

"In the year to May 2015, IS took over another 10 to 15% of Syrian territory, and they still hold significant swaths of land in Iraq and Syria.

"When the Iraqi town of Mosul was captured, you only had 800 members of IS that couldn't be beaten by thousands of Iraqi security forces.

"These IS members are much more militarised than other terrorist organisations. Many will be ex-military."

How much support do they have there?

"I think the majority of people under their control are scared. Coercion is one of the biggest tools they have through military tactics and propaganda.

"They send messages out to the towns they're going to target to warn them they're on the way.

"That's a massive scare factor. It promotes the idea it's easier for these people to flee these towns or submit to the will of IS.

"They're also forcing citizens to become part of the organisation in order to protect their families."

It's estimated around 70% of members are forced into to join.

How effective have US-led airstrikes been?

"At the moment, we're playing catch up with the organisation. It's a cat and mouse game and I think we're the ones trailing behind.

"Airstrikes are having an impact but I don't think they're having as significant an impact as we would hope.

"They spread out into little pockets are constantly on the move.

"It's very hard for us to get a full picture of where they actually are in terms of their key bases and there's no one specific location.

"The airstrikes have to be very targeted. Every time we have 'collateral damage' - civilians killed by the airstrikes - we're feeding into IS's propaganda machine."

But IS are losing fighters every day, aren't they?

"Yes but the turnaround is quite quick in terms of membership.

"They still have a significant enough support base to replenish their ranks. We have them coming from Australia, UK, Germany, France... and the local people being forced to join.

"But we're not sure how long they can actually keep up that replenishment if our counter campaign increases and we make inroads targeting those 'foot soldiers'."

So could it really just take just months to defeat them?

"I think months is under playing the significance of IS. I don't think it'll take a generation but I do think we're talking years.

"Airstrikes alone are not going to wipe out this organisation.

"We need to work more closely with neighbouring countries in the region so we have a clearer idea what's going on.

"I think we may end up seeing some sort of boots on the ground scenario in the near future - but not necessarily US or UK troops."

A Foreign Office Spokesman said: "It's clear that overall, the Global Coalition is pushing Isil (another name for IS) back.

"The action being taken by the coalition, in support of Iraqi security forces, has liberated key towns.

"IS has now lost more than 30% of the territory it once held there."

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